Debugging, the Developer Way

Transcript

1. Debugging, the Developer Way Yarden Laifenfeld @yardenlaif
2. 2 Who Am I? • Software Engineer at Rookout • Go, Java, Ruby • C#, Python, JavaScript, C++ • Sewing
3. Non Breaking Breakpoints 3
4. 4 I love debugging. wtf?
6. 6 1/30
7. 7 50%
8. Why? 8 • We don’t know how • Intuition • It’s not fun • Simple code == simple bugs
9. The Flow 9 • Unexpected behavior • What/Why/Where? • Fix
10. Unexpected Behavior 10 • Incorrect use
11. UI/UX Issue 11 CLICK ME DON’T CLICK ME
12. Bad Response 12 CLICK ME DON’T CLICK ME
13. Unexpected Behavior 13 • Incorrect use • Something went terribly wrong
14. Something Went Terribly Wrong 14
15. Unexpected Behavior 15 • Incorrect use • Something went terribly wrong • Integration Issues
16. Integration Issues 16
17. Unexpected Behavior 17 • Incorrect use • Something went terribly wrong • Integration Issues • Expectation ≠ Reality
18. What/Why/Where 18 • Stare at the code • Read all the logs • Try to reproduce • Run through each line of code
19. Fix 19 • Find a way to fix • Write the code • Add a test
20. The “Research Based” Flow 20 • Our code is a mystery • No planning • Guessing randomly ◦ print debugging
21. 21 Approach debugging like writing a feature
22. Writing a Feature 22 • Specification • Planning • Executing
23. Specification 23 • Get all the information ◦ Understand the task ◦ Edge cases ◦ Protocols • Definition of done
24. Planning - Design the Feature 24 • Components • Language to use • Design patterns • Third party libraries
25. Planning - Deadlines 25 • Multiple deadlines • What if I miss the deadline?
26. Planning - Setup Your Workspace 26 • An easy-to-run example • Up to date code • Comfortable environment
27. Executing 27 • Develop in iterations • Document as you code
28. Writing a Feature 28 • Specification ◦ Get all the information ◦ Definition of done • Planning ◦ Design the feature ◦ Deadlines ◦ Setup your workplace • Executing ◦ Develop in iterations ◦ Document as you code
29. Debugging a Bug 29 • Specification • Planning • Executing
30. Specification - Get All the Information • Is it even a bug? • Logs, Traces, Metrics • Environment 30 ➔ Specification ➔ Planning ➔ Executing
31. Specification - Definition of Done • Reproduction • How do I know I fixed the bug? 31 ➔ Specification ➔ Planning ➔ Executing
32. Planning - Design the Debugging Process • If I wanted to purposefully create this bug, how would I do that? • Multiple debugging vectors ◦ Practical milestones 32 ➔ Specification ➔ Planning ➔ Executing
33. Planning - Deadlines • Multiple deadlines • What if I miss the deadline? 33 ➔ Specification ➔ Planning ➔ Executing
34. Planning - Setup Your Workspace 34 • An easy-to-run example • Relevant code version • Comfortable environment ➔ Specification ➔ Planning ➔ Executing
35. Executing - Use the Right Tools • Print debugging • Debuggers • Profilers 35 ➔ Specification ➔ Planning ➔ Executing
36. Executing - Debug in Iterations • Practical milestones • Make sure you’re making progress • Validate your assumptions • Commit to git 36 ➔ Specification ➔ Planning ➔ Executing
37. Executing - Document EVERYTHING • Document things that worked • Document things that didn’t • Document your thoughts • Document consistently and clearly 37 ➔ Specification ➔ Planning ➔ Executing
38. Executing - Find and Fix Once you’ve found the bug, go back to the specification step 38 ➔ Specification ➔ Planning ➔ Executing
39. Debugging a Bug 39 • Specification ◦ Get all the information ◦ Definition of done • Planning ◦ Design the debugging process ◦ Deadlines ◦ Setup your workplace • Executing ◦ Develop in iterations ◦ Document as you debug ◦ Use the right tools ◦ Fix the bug
40. 40 Plan Proportionately
41. 41 Let’s See it in Action!
44. 44 Seats DB getAvailableSeats() reserve(id, seats) checkout(id) cancel(id)
45. Seat Selection Flow 45 • UserCart calls DB.reserve(id, seats) • DB checks if seats are available: ◦ Not available: throws an error ◦ Available: marks seats as reserved ▪ Previous seats are discarded • UserCart adds seats to list of reserved seats
46. 46 func select_seat(seat) { thread { new_seats = this.seats + seat serialized = new_seats.serialize() try { db.reserve(this.id, serialized) this.seats.add(seat) } } }
47. Checkout Seat Flow 47 • UserCart calls DB.checkout (id) • DB marks all reserved seats associated with id as taken • UserCart sends tickets for all seats in list of reserved seats
48. 48 func checkout() { db.checkout(this.id) send_tickets(this.seats) }
49. Bug 49 Alice and Bob arrive at the movie theater with tickets for the same seat (A3).
50. Specification - Get All the Information • Doubt the user • Logs 50 ➔ Specification ➔ Planning ➔ Executing
51. Specification - Logs 51
52. Specification - Definition of Done • Reproduction • How do I know I fixed the bug? 52 ➔ Specification ➔ Planning ➔ Executing
53. Specification - Reproduction 53
54. Planning - Design the Debugging Process • If I wanted to purposefully create this bug, how would I do that? • Multiple debugging vectors ◦ Practical milestones 54 ➔ Specification ➔ Planning ➔ Executing
55. Checkout Seat Flow 55 Seat Selection • UserCart calls DB.reserve(id, seats) • DB checks if seats are available: ◦ Not available: throws an error ◦ Available: marks seats as reserved (previous seats are discarded) • UserCart adds seats to list of reserved seats Checkout • UserCart calls DB.checkout(id) • DB marks all reserved seats associated with id as taken • UserCart sends tickets for all seats in list of reserved seats
56. Planning - Debugging Vectors • DB.reserve doesn’t reserve seats • UserCart sends the wrong seats to reserve • DB doesn’t checkout the correct seats • DB doesn’t mark reserved seats as taken correctly • UserCart sends tickets for wrong seats 56 ➔ Specification ➔ Planning ➔ Executing
57. Planning - Debugging Vectors 1. DB doesn’t mark reserved seats as taken correctly 2. DB doesn’t checkout the correct seats 3. DB.reserve doesn’t reserve seats 57 ➔ Specification ➔ Planning ➔ Executing
58. Planning - Practical Milestones 1. DB doesn’t mark reserved seats as taken correctly a. Sanity check DB.checkout() b. Stress check DB.checkout() 2. DB doesn’t checkout the correct seats a. Verify UserCart and DB mark the same seats at checkout 3. DB.reserve doesn’t reserve seats 58 ➔ Specification ➔ Planning ➔ Executing
59. Planning - Deadlines 1. DB doesn’t mark reserved seats as taken correctly a. Sanity check DB.checkout() - 2 min. b. Stress check DB.checkout() - 5 min. 2. DB doesn’t checkout the correct seats a. Verify UserCart and DB mark the same seats at checkout - 10 min. 3. DB.reserve doesn’t reserve seats 59 ➔ Specification ➔ Planning ➔ Executing
60. Planning - Setup Your Workspace 60 • An easy-to-run example • Relevant code version • Comfortable environment ➔ Specification ➔ Planning ➔ Executing
61. Executing • Use the right tools • Debug in iterations • Document EVERYTHING • Find and fix 61 ➔ Specification ➔ Planning ➔ Executing
62. Executing 1. DB doesn’t mark reserved seats as taken correctly a. Sanity check DB.checkout() ✔ b. Stress check DB.checkout() ✔ 2. DB doesn’t checkout the correct seats a. Verify UserCart and DB mark the same seats at checkout 3. DB.reserve doesn’t reserve seats 62 ➔ Specification ➔ Planning ➔ Executing
63. Verify UserCart and DB mark the same seats at checkout 63
64. The Bug & The Fix • Try it yourself! • Solution: @yardenlaif 64
65. 65 Have Fun!
66. Thank You @yardenlaif hachyderm.io/@yarden yardenlaif.com